A spectroscopic investigation of novel doped glasses for active infrared devices

Aronson, Jonathan Edward (2006) A spectroscopic investigation of novel doped glasses for active infrared devices. University of Southampton, Optoelectronics Research Centre, Doctoral Thesis, 195pp.

Record type: Thesis (Doctoral)

Abstract

A number of novel doped glasses have been studied for their potential as infrared amplifier materials. Optical amplifiers which operate outside of the C-band are likely to form part of future optical telecoms systems. This work is focused on transition metal and rare earth-doped materials which could provide gain in the telecoms S-band. Nickel and Vanadium-doped gallium lanthanum sulphide (GLS) glasses were identified as possible new amplifier materials. Emission was observed at 1200nm from Ni-doped GLS and at 1400nm for V-doped GLS. The FWHM of the emission from V-doped GLS was 450 nm, making it particularly attractive for a broadband optical amplifier. Low temperature emission spectra from V-doped GLS suggest that it is not affected by nonradiative decay to the same extent as Cr-doped GLS. Thulium and erbium-doped tin silicate glass-ceramics produced by the sol-gel method were studied for as potential amplifier materials. The addition of tin oxide to these glasses makes them photosensitive and is shown in this work to increase fluorescence lifetimes. However, the addition of >5% SnO₂ causes increased infrared absorption which would outweigh advantages gained by the increased lifetime. Thulium-doped tin silicate glass-ceramics were investigated for the first time, and show a broad fluorescence band at 1470 nm with a FWHM of ~120 nm. The maximum lifetime of the ³F₄ level was 37 µs, which is higher than in Tm-doped silica. Y₂O₃-Al₂O₃-SiO₂ (YAS) glass was investigated as a low phonon silicate host for a thulium-doped fibre amplifier. Raman and FTIR measurements showed that the maximum phonon energy can be reduced by increasing the yttria:alumina ratio and decreasing the silica content. This was confirmed by emission lifetime measurements of the ³F₄ level, which showed an increase in lifetime of 20% over the range studied. A Tm-doped YAS fibre was successfully drawn from a glass of the composition 17.4% Y₂O₃, 22.5% Al₂O₃ and 60% SiO₂. 7.5 m of continuous unclad fibre was fabricated with a diameter of 150-350 µm at a temperature of 1150°C. The minimum loss in the fibre was measured to be 3.6 dB/m at 1360 nm. This material is shown to have good potential for use in S-band fibre amplification.